Agalsidase alfa versus agalsidase beta for the treatment of Fabry disease: an international cohort study.

BACKGROUND: Two recombinant enzymes (agalsidase alfa 0.2 mg/kg/every other week and agalsidase beta 1.0 mg/kg/every other week) have been registered for the treatment of Fabry disease (FD), at equal high costs. An independent international initiative compared clinical and biochemical outcomes of the two enzymes. METHODS: In this multicentre retrospective cohort study, clinical event rate, left ventricular mass index (LVMI), estimated glomerular filtration rate (eGFR), antibody formation and globotriaosylsphingosine (lysoGb3) levels were compared between patients with FD treated with agalsidase alfa and beta at their registered dose after correction for phenotype and sex. RESULTS: 387 patients (192 women) were included, 248 patients received agalsidase alfa. Mean age at start of enzyme replacement therapy was 46 (±15) years. Propensity score matched analysis revealed a similar event rate for both enzymes (HR 0.96, P=0.87). The decrease in plasma lysoGb3 was more robust following treatment with agalsidase beta, specifically in men with classical FD (ß: -18 nmol/L, P<0.001), persisting in the presence of antibodies. The risk to develop antibodies was higher for patients treated with agalsidase beta (OR 2.8, P=0.04). LVMI decreased in a higher proportion following the first year of agalsidase beta treatment (OR 2.27, P=0.03), while eGFR slopes were similar. CONCLUSIONS: Treatment with agalsidase beta at higher dose compared with agalsidase alfa does not result in a difference in clinical events, which occurred especially in those with more advanced disease. A greater biochemical response, also in the presence of antibodies, and better reduction in left ventricular mass was observed with agalsidase beta.

Adaptive pathway development for Fabry disease: a clinical approach.

Fabry disease (FD) is a rare X-chromosome-linked lysosomal storage disorder. Although initial expectations of enzyme replacement therapy (ERT) were high, it is now clear that real-world effectiveness is disappointing and evidence gathering has been inadequate. In retrospect, development of ERT for FD had several shortcomings. Little convincing evidence on the effectiveness existed at time of authorization. Also, post-marketing evaluation failed to generate sufficient and relevant data for adequate evaluation on effectiveness. Adaptive pathways might have benefitted ERT development by: (i) involving healthcare professionals, patients, health technology assessment bodies and payers in the development process; (ii) iterative development, starting with initial authorization in classical males; (iii) a clear real-world data collection plan; (iv) an independent disease registry; and (v) prescription control.

Phenotype, disease severity and pain are major determinants of quality of life in Fabry disease: results from a large multicenter cohort study.

Quality of life (QoL) is decreased in patients with Fabry disease (FD). To improve QoL, it is important to understand the influence of FD related characteristics, symptoms, and complications. In this retrospective cohort study we explored the effect of pain (measured by the Brief Pain Inventory), phenotype, treatment, and FD-related complications on QoL. QoL data of Fabry patients as assessed by the EuroQol five dimension questionnaire (EQ-5D) from two international centers of excellence were collected. The aim of this study was to evaluate the effect of sex, phenotype, age, different states of disease severity, pain, and ERT on EQ-5D utilities. For 286 adult FD patients (mean age 42.5 years, 40% men, 60% classical phenotype) 2240 EQ-5Ds were available. QoL is decreased in men as well as women with FD, especially in older men with a classical phenotype. At age 50, utility was lower in men with classical FD compared to those with non-classical disease (ß = -0.12, 95% CI: -0.23 - 0.01, p = 0.037) with further difference in the years thereafter. Cardiovascular complications, stroke or transient ischemic attacks, multiple FD-related complications and pain were also associated with decreased utilities. Overall, no change in utility was seen in patients on ERT over a mean follow-up of 6.1 years. FD leads to a decreased QoL compared to the general population. Disease complications and pain both negatively influence QoL. Adequate assessment and treatment of pain as well as improved strategies to prevent disease complications are needed to improve QoL in the FD population.

Retrospective study of long-term outcomes of enzyme replacement therapy in Fabry disease: Analysis of prognostic factors.

Despite enzyme replacement therapy, disease progression is observed in patients with Fabry disease. Identification of factors that predict disease progression is needed to refine guidelines on initiation and cessation of enzyme replacement therapy. To study the association of potential biochemical and clinical prognostic factors with the disease course (clinical events, progression of cardiac and renal disease) we retrospectively evaluated 293 treated patients from three international centers of excellence. As expected, age, sex and phenotype were important predictors of event rate. Clinical events before enzyme replacement therapy, cardiac mass and eGFR at baseline predicted an increased event rate. eGFR was the most important predictor: hazard ratios increased from 2 at eGFR <90 ml/min/1.73m2 to 4 at eGFR <30, compared to patients with an eGFR >90. In addition, men with classical disease and a baseline eGFR <60 ml/min/1.73m2 had a faster yearly decline (-2.0 ml/min/1.73m2) than those with a baseline eGFR of >60. Proteinuria was a further independent risk factor for decline in eGFR. Increased cardiac mass at baseline was associated with the most robust decrease in cardiac mass during treatment, while presence of cardiac fibrosis predicted a stronger increase in cardiac mass (3.36 gram/m2/year). Of other cardiovascular risk factors, hypertension significantly predicted the risk for clinical events. In conclusion, besides increasing age, male sex and classical phenotype, faster disease progression while on enzyme replacement therapy is predicted by renal function, proteinuria and to a lesser extent cardiac fibrosis and hypertension.

Favourable effect of early versus late start of enzyme replacement therapy on plasma globotriaosylsphingosine levels in men with classical Fabry disease.

BACKGROUND: The level of plasma globotriaosylsphingosine (lysoGb3) is an indication of disease severity in Fabry disease (FD) and its decrease during enzyme replacement therapy could be a reflection of treatment efficacy. Early treatment of FD may improve clinical outcome, but data to support this hypothesis are scarce. In this study we compared lysoGb3 decrease after ERT initiation in men with classical FD who started ERT before the age of 25 (early-treatment) with those who started later in life (late-treatment). METHODS: Treatment naïve men with classical FD from three centers of excellence in Europe were included. Measurements of lysoGb3 levels by tandem mass spectroscopy and antibodies by an inhibitory assay were performed in a single laboratory. Results were adjusted for lysoGb3 at baseline, first ERT (i.e. agalsidase alfa or beta) and the average ERT dose. RESULTS: 85 patients were included, 21 in the early-treatment and 64 in the late-treatment group. LysoGb3 level at baseline was not different between the two groups (112 vs 114nmol/L, p=0.92). The adjusted odds ratio for reaching a lysoGb3 level<20nmol/L was 7.38 for the early-treatment versus late-treatment group (95% CI: 1.91-34.04, p=0.006). The adjusted lysoGb3 levels one year after ERT initiation was 12.9nmol/L lower in the early-treatment (95% CI: -20.1--5.8, p<0.001) compared to the late-treatment group. CONCLUSION: The current retrospective cohort study shows that initiation of ERT at younger age in men with classical Fabry disease results in a better biochemical response.

Characterization of Classical and Nonclassical Fabry Disease: A Multicenter Study.

Fabry disease leads to renal, cardiac, and cerebrovascular manifestations. Phenotypic differences between classically and nonclassically affected patients are evident, but there are few data on the natural course of classical and nonclassical disease in men and women. To describe the natural course of Fabry disease stratified by sex and phenotype, we retrospectively assessed event-free survival from birth to the first clinical visit (before enzyme replacement therapy) in 499 adult patients (mean age 43 years old; 41% men; 57% with the classical phenotype) from three international centers of excellence. We classified patients by phenotype on the basis of characteristic symptoms and enzyme activity. Men and women with classical Fabry disease had higher event rate than did those with nonclassical disease (hazard ratio for men, 5.63, 95% confidence interval, 3.17 to 10.00; P<0.001; hazard ratio for women, 2.88, 95% confidence interval, 1.54 to 5.40; P<0.001). Furthermore, men with classical Fabry disease had lower eGFR, higher left ventricular mass, and higher plasma globotriaosylsphingosine concentrations than men with nonclassical Fabry disease or women with either phenotype (P<0.001). In conclusion, before treatment with enzyme replacement therapy, men with classical Fabry disease had a history of more events than men with nonclassical disease or women with either phenotype; women with classical Fabry disease were more likely to develop complications than women with nonclassical disease. These data may support the development of new guidelines for the monitoring and treatment of Fabry disease and studies on the effects of intervention in subgroups of patients.

Discontinuation of enzyme replacement therapy in Fabry disease in the Dutch cohort.

Fabry disease (FD) is a progressive, multi-organ, lysosomal storage disease. Enzyme replacement therapy (ERT) is available for the treatment of the disease. While the reasons to initiate ERT have been frequently discussed, discontinuation of ERT is rarely reported. In this paper we describe our experiences with stopping ERT in FD. From 1999 through 2015, twenty-one patients discontinued ERT. These patients were generally older and more severely affected in comparison those who continued ERT. The reason to discontinue ERT switched from death or terminal illness in the first years towards treatment failure in more recent years. Three cases are described in more detail. We conclude that discontinuation of ERT should or may be considered in subgroups of FD patients although further studies on the effectiveness of ERT in subgroups of patients and the course of the disease after discontinuation of ERT are needed.

Quality of life in patients with Fabry disease: a systematic review of the literature.

Fabry disease (FD), caused by deficiency of the lysosomal enzyme α-galactosidase-A, is a progressive multisystem disease. The disease is X-linked with generally more severe manifestations in males, but can impact on quality of life (QoL) of both male and female patients. The purpose of this literature review is to analyse the currently available data concerning QoL measurement, specifically which questionnaires have been used to measure QoL, how patients with FD score compared to the general population, and the effects of enzyme replacement therapy (ERT) on QoL. Fifty-four articles were relevant for this literature review. Patients with FD had a lower QoL compared to the general population. No definite conclusions could be drawn from the studies on the effect of ERT on QoL; natural history data is scarce, changes observed were limited and the cohorts were of small size. We propose that a FD specific questionnaire be made to accurately assess QoL in patients with FD.

Malignancies and monoclonal gammopathy in Gaucher disease; a systematic review of the literature.

Gaucher disease is an autosomal, recessively inherited, lysosomal storage disease, which has been associated with gammopathies and malignancies. This report represents the results of a systematic review of the literature on the prevalence of monoclonal gammopathies and malignancies in Gaucher disease. A PubMed search identified 365 studies, of which 80 reported on concomitant Gaucher disease and malignancies and/or gammopathies (15 cohort/cross sectional studies, and 65 case reports/series). Based on these studies, we conclude that compared to the general population, Gaucher patients have an increased risk of cancer in general [pooled relative risk of 1·70 (95% confidence interval 1·27-2·31)], and multiple myeloma and haematological malignancies in particular (estimated risk between 25·0 and 51·1 and 3·5 and 12·7, respectively). In addition, an increased risk has been reported for hepatocellular carcinoma and renal cell carcinoma. Several factors have been hypothesized to play a role in the pathophysiology. These include: splenectomy, immune dysregulation, endoplasmic reticulum stress, genetic modifiers, altered iron metabolism and insulin resistance.

Identification of novel mutations in patients with Leber congenital amaurosis and juvenile RP by genome-wide homozygosity mapping with SNP microarrays.

PURPOSE: Leber congenital amaurosis (LCA) and juvenile retinitis pigmentosa (RP) cause severe visual impairment early in life. Thus far, mutations in 13 genes have been associated with autosomal recessive LCA and juvenile RP. The purpose of this study was to use homozygosity mapping to identify mutations in known LCA and juvenile RP genes. METHODS: The genomes of 93 consanguineous and nonconsanguineous patients with LCA and juvenile RP were analyzed for homozygous chromosomal regions by using SNP microarrays. This patient cohort was highly selected, as mutations in the known genes had been excluded with the LCA mutation chip, or a significant number of LCA genes had been excluded by comprehensive mutation analysis. Known LCA and juvenile RP genes residing in the identified homozygous regions were analyzed by sequencing. Detailed ophthalmic examinations were performed on the genotyped patients. RESULTS: Ten homozygous mutations, including seven novel mutations, were identified in the CRB1, LRAT, RPE65, and TULP1 genes in 12 patients. Ten patients were from consanguineous marriages, but in two patients no consanguinity was reported. In 10 of the 12 patients, the causative mutation was present in the largest or second largest homozygous segment of the patient's genome. CONCLUSIONS: Homozygosity mapping using SNP microarrays identified mutations in a significant proportion (30%) of consanguineous patients with LCA and juvenile RP and in a small number (3%) of nonconsanguineous patients. Significant homozygous regions which did not map to known LCA or juvenile RP genes and may be instrumental in identifying novel disease genes were detected in 33 patients.

FERM protein EPB41L5 is a novel member of the mammalian CRB-MPP5 polarity complex.

Cell polarity is induced and maintained by separation of the apical and basolateral domains through specialized cell-cell junctions. The Crumbs protein and its binding partners are involved in formation and stabilization of adherens junctions. In this study, we describe a novel component of the mammalian Crumbs complex, the FERM domain protein EPB41L5, which associates with the intracellular domains of all three Crumbs homologs through its FERM domain. Surprisingly, the same FERM domain is involved in binding to the HOOK domain of MPP5/PALS1, a previously identified interactor of Crumbs. Co-expression and co-localization studies suggested that in several epithelial derived tissues Epb4.1l5 interacts with at least one Crumbs homolog, and with Mpp5. Although at early embryonic stages Epb4.1l5 is found at the basolateral membrane compartment, in adult tissues it co-localizes at the apical domain with Crumbs proteins and Mpp5. Overexpression of Epb4.1l5 in polarized MDCK cells affects tightness of cell junctions and results in disorganization of the tight junction markers ZO-1 and PATJ. Our results emphasize the importance of a conserved Crumbs-MPP5-EPB41L5 polarity complex in mammals.

Novel compound heterozygous TULP1 mutations in a family with severe early-onset retinitis pigmentosa.

OBJECTIVE: To describe the clinical characteristics and determine the genetic defect in a Surinamese family with autosomal recessive retinitis pigmentosa. METHODS: Family members underwent blood sampling and ophthalmologic examinations. After exclusion of all known mutations in all genes involved in autosomal recessive retinitis pigmentosa, a genome-wide linkage scan was performed using 11,555 single-nucleotide polymorphisms spread throughout the genome. Mutation analysis of the TULP1 gene was performed by direct sequencing. RESULTS: All affected family members had a severe retinal dystrophy with a history of nystagmus, low visual acuity, and nyctalopia since infancy. The scotopic and photopic responses were nonrecordable on electroretinography. A genome-wide scan suggested linkage to the chromosomal region containing the TULP1 gene. Mutation analysis of TULP1 identified novel compound heterozygous mutations (p.Arg482Trp and p.Leu504fsX140) in all affected family members. CONCLUSIONS: The affected members of the Surinamese family have a severe early-onset form of autosomal recessive retinitis pigmentosa, which is caused by compound heterozygous mutations in the TULP1 gene. Clinical Relevance Clinical and molecular genetic characterization of autosomal recessive retinitis pigmentosa may help to provide a more accurate prognosis in individual patients. This study confirms that TULP1 mutations cause a severe early-onset form of autosomal recessive retinitis pigmentosa.

Mutations in the CEP290 (NPHP6) gene are a frequent cause of Leber congenital amaurosis.

Leber congenital amaurosis (LCA) is one of the main causes of childhood blindness. To date, mutations in eight genes have been described, which together account for approximately 45% of LCA cases. We localized the genetic defect in a consanguineous LCA-affected family from Quebec and identified a splice defect in a gene encoding a centrosomal protein (CEP290). The defect is caused by an intronic mutation (c.2991+1655A-->G) that creates a strong splice-donor site and inserts a cryptic exon in the CEP290 messenger RNA. This mutation was detected in 16 (21%) of 76 unrelated patients with LCA, either homozygously or in combination with a second deleterious mutation on the other allele. CEP290 mutations therefore represent one of the most frequent causes of LCA identified so far.

Characterization of the Crumbs homolog 2 (CRB2) gene and analysis of its role in retinitis pigmentosa and Leber congenital amaurosis.

PURPOSE: Mutations in the Crumbs homolog 1 (CRB1) gene cause autosomal recessive retinitis pigmentosa (RP) and Leber congenital amaurosis (LCA). Database searches reveal two other Crumbs homologs on chromosomes 9q33.3 and 19p13.3. The purpose of this study was to characterize the Crumbs homolog 2 (CRB2) gene on 9q33.3, to analyze its expression pattern, and to determine whether mutations in CRB2 are associated with RP and LCA. METHODS: The CRB2 mRNA and its expression pattern in human tissues were analyzed by reverse transcription-polymerase chain reaction (RT-PCR). The cellular expression of Crb2 in the mouse eye was determined by mRNA in situ hybridizations. The open reading frame and splice junctions of CRB2 were analyzed for mutations by single-strand conformation analysis and direct nucleotide sequencing in 85 RP patients and 79 LCA patients. RESULTS: The CRB2 gene consists of 13 exons and encodes a 1285 amino acid transmembrane protein. CRB2 is mainly expressed in retina, brain, and kidney. In mouse retina Crb2 expression was detected in all cell layers. Mutation analysis of the CRB2 gene revealed 11 sequence variants leading to an amino acid substitution. Three of them were not identified in control individuals and affect conserved amino acid residues. However, the patients that carry these sequence variants do not have a second sequence variant on the other allele, excluding autosomal recessive inheritance of CRB2 sequence variants as a cause of their disease. CONCLUSIONS: This study shows that CRB2 sequence variants are not a common cause of autosomal recessive RP and LCA. It is possible that a more complex clinical phenotype is associated with the loss or altered function of CRB2 in humans due to its expression in tissues other than the retina.